U.S. patent number 8,396,422 [Application Number 11/550,323] was granted by the patent office on 2013-03-12 for communication control device, method of determining communication control device, and storage medium for performing the method.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is Tetsuo Kanda, Atsushi Takasaki. Invention is credited to Tetsuo Kanda, Atsushi Takasaki.
United States Patent |
8,396,422 |
Takasaki , et al. |
March 12, 2013 |
Communication control device, method of determining communication
control device, and storage medium for performing the method
Abstract
A device and method for controlling communication among a
plurality of communication devices, the device and method including
causing each of one or more candidate devices to which control
rights of a network are transferable, from among the plurality of
communication devices, to transmit a pseudo information signal,
counting, for each of the one or more candidate devices, the number
of communication devices from the plurality of communication
devices having responded to the pseudo information signal, and
determining a candidate device to which to transfer control rights
of the network based on the number of communication devices from
the plurality of communication devices having responded to the
pseudo information signal.
Inventors: |
Takasaki; Atsushi (Kawasaki,
JP), Kanda; Tetsuo (Kawasaki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Takasaki; Atsushi
Kanda; Tetsuo |
Kawasaki
Kawasaki |
N/A
N/A |
JP
JP |
|
|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
38024205 |
Appl.
No.: |
11/550,323 |
Filed: |
October 17, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070100983 A1 |
May 3, 2007 |
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Foreign Application Priority Data
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Oct 31, 2005 [JP] |
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2005-317113 |
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Current U.S.
Class: |
455/41.2;
370/350; 709/226; 709/223; 370/331 |
Current CPC
Class: |
H04W
24/00 (20130101); H04W 48/16 (20130101); H04W
48/20 (20130101); H04W 84/18 (20130101); H04W
8/005 (20130101); H04W 84/10 (20130101) |
Current International
Class: |
H04B
7/00 (20060101) |
Field of
Search: |
;455/41.2 ;709/223 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-223217 |
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Aug 2002 |
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JP |
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2003-273883 |
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Sep 2003 |
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JP |
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2004-254048 |
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Sep 2004 |
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JP |
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2005-027280 |
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Jan 2005 |
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JP |
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2005-275539 |
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Oct 2005 |
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JP |
|
Other References
H Jeong, M. Cho, S. Kim, D. Kim, and J. Lee; "PNC Candidate Inquiry
Method for PNC Handover on WPAN," Personal, Inidoor and Mobile
Radio Communications, 2004. PIMRC 2004. 15.sup.th IEEE
International Symposium on Barelona Spain Sep. 5-8, 2004,
Pistacataway, NJ, USA, IEEE, vol. 3 pp. 1752-1765. cited by
examiner .
IEEE Std. 802.15.3-2003, IEEE, 2003, (Section 1, 5, and 8.2.3).
cited by applicant.
|
Primary Examiner: Maung; Nay A
Assistant Examiner: Fleming-Hall; Erica
Attorney, Agent or Firm: Canon USA Inc. IP Division
Claims
What is claimed is:
1. A communication apparatus comprising: a storage unit configured
to store information indicating a plurality of other communication
apparatuses participating in a network managed by the communication
apparatus; an instruction unit configured to instruct a first
communication apparatus to transmit a first signal, wherein the
first signal is a signal for causing an apparatus that has received
the first signal to transmit a second signal to the communication
apparatus; a receiving unit configured to receive the second signal
from at least one apparatus that receives the first signal from the
first communication apparatus; a determination unit configured to
determine, based on the information stored in the storage unit and
a result of reception by the receiving unit, whether the receiving
unit has received the second signal from the plurality of other
communication apparatuses; and a request unit configured to request
the first communication apparatus to manage the network according
to a result of determination by the determination unit.
2. The communication apparatus according to claim 1, wherein the
storage unit further stores specification information for
specifying the first communication apparatus, and wherein the
instruction unit instructs the first communication apparatus to
transmit the first signal based on the specification information
stored in the storage unit.
3. The communication apparatus according to claim 1, wherein the
request unit requests the first communication apparatus to manage
the network prior to termination of control of the network by the
communication apparatus.
4. The communication apparatus according to claim 1, wherein the
first signal comprises network identification information for
identifying the network and apparatus information of an apparatus
having transmitted the first signal, and wherein another
communication apparatus that has received the first signal
transmits the second signal in a case where the first signal
received by the another communication apparatus comprises the
network identification information of a network in which the
another communication apparatus participates and apparatus
information which indicates an apparatus different from the
communication apparatus.
5. The communication apparatus according to claim 1, wherein the
instruction unit instructs the first communication apparatus to
transmit the first signal during a period when the communication
apparatus is to transmit an annunciation signal for network
synchronization.
6. The communication apparatus according to claim 1, wherein the
first signal comprises same network information as an information
signal for network synchronization transmitted from the
communication apparatus.
7. A communication method for a communication apparatus, the method
comprising steps of: storing information indicating a plurality of
other communication apparatuses participating in a network managed
by the communication apparatus; instructing a first communication
apparatus to transmit a first signal, wherein the first signal is a
signal for causing an apparatus that has received the first signal
to transmit a second signal to the communication apparatus;
receiving the second signal from at least one apparatus that
receives the first signal from the first communication apparatus;
determining, based on the stored information and a result of
reception, whether the second signal has been received from the
plurality of other communication apparatuses; and requesting the
first communication apparatus to manage the network according to a
result of determination.
8. The communication method according to claim 7, further
comprising steps of: storing specification information for
specifying the first communication apparatus; and instructing the
first communication apparatus to transmit the first signal based on
the stored specification information.
9. The communication method according to claim 7, further
comprising requesting the first communication apparatus to manage
the network prior to termination of control of the network by the
communication apparatus.
10. The communication method according to claim 7, wherein the
first signal comprises network identification information for
identifying the network and apparatus information of an apparatus
having transmitted the first signal, and wherein another
communication apparatus that has received the first signal
transmits the second signal in a case where the first signal
received by the another communication apparatus comprises the
network identification information of a network in which the
another communication apparatus participates and apparatus
information which indicates an apparatus different from the
communication apparatus.
11. The communication method according to claim 7, wherein the
instructing step instructs the first communication apparatus to
transmit the first signal during a period when the communication
apparatus is to transmit an annunciation signal for network
synchronization.
12. The communication method according to claim 7, wherein the
first signal comprises same network information as an information
signal for network synchronization transmitted from the
communication apparatus.
13. A non-transitory computer-readable storage medium storing
computer-executable process steps for controlling a communication
apparatus, the computer-executable process steps comprising:
storing information indicating a plurality of other communication
apparatuses participating in a network managed by the communication
apparatus; instructing a first communication apparatus to transmit
a first signal, wherein the first signal is a signal for causing an
apparatus that has received the first signal to transmit a second
signal to the communication apparatus; receiving the second signal
from at least one apparatus that receives the first signal from the
first communication apparatus; determining, based on the stored
information and a result of reception, whether the second signal
has been received from the plurality of other communication
apparatuses; and requesting the first communication apparatus to
manage the network according to a result of determination.
14. The non-transitory computer-readable storage medium according
to claim 13, the computer-executable process steps further
comprising: storing specification information for specifying the
first communication apparatus; and instructing the first
communication apparatus to transmit the first signal based on the
stored specification information.
15. The non-transitory computer-readable storage medium according
to claim 13, the computer-executable process steps further
comprising requesting the first communication apparatus to manage
the network prior to termination of control of the network by the
communication apparatus.
16. The non-transitory computer-readable storage medium according
to claim 13, wherein the first signal comprises network
identification information for identifying the network and
apparatus information of an apparatus having transmitted the first
signal, and wherein another communication apparatus that has
received the first signal transmits the second signal in a case
where the first signal received by the another communication
apparatus comprises the network identification information of a
network in which the another communication apparatus participates
and apparatus information which indicates an apparatus different
from the communication apparatus.
17. The non-transitory computer-readable storage medium according
to claim 13, wherein the instructing step instructs the first
communication apparatus to transmit the first signal during a
period when the communication apparatus is to transmit an
annunciation signal for network synchronization.
18. The non-transitory computer-readable storage medium according
to claim 13, wherein the first signal comprises same network
information as an information signal for network synchronization
transmitted from the communication apparatus.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to techniques of transferring control
rights of communication among a plurality of communication
devices.
2. Description of the Related Art
IEEE802.15.3 (see IEEE Std. 802.15.3-2003, IEEE, 2003) is a Medium
Access Control (MAC) standard for Wireless Personal Area Networks
(WPANs) . This standard is specialized for WPANs and has an
advantage in enabling simplification of the configuration of
network devices, as compared with local area network (LAN)
standards.
According to a wireless communication system conforming to the
IEEE802.15.3 standard, in each piconet including one or more
devices, one device serving as a control device is present and
controls traffic in the piconet. However, because it is assumed
that devices relatively frequently join and leave the piconet, the
control device is not fixedly provided therein. A control rights
transfer process of transferring control rights to a piconet device
differing from the current control device is performed, for
example, in a case where a piconet device, which is superior in
functions and performance, such as the number of controllable
devices, to a current control device, newly joins the piconet, or
where the current control device leaves the piconet for some
reason. The piconet can continuously be maintained by performing
the control rights transfer process. The control rights transfer
process is described in detail in Section 8.2.3 "PNC Handover" in
IEEE Std. 802.15.3-2003, IEEE, 2003.
However, when performing the process of transferring control rights
to a device, which is determined according to the function and the
level of performance, as described above, in many instances the
wireless communication system has encountered a problem that a
piconet device may be unable to continue to join the piconet.
FIG. 1 illustrates a positional relationship among a piconet
coordinator (PNC) 101, which is a piconet device enabled to serve
as a control device, and other piconet devices (DEVs) 111 to 114,
which do not serve as a control device, in a piconet. The PNC 101
controls/manages the DEVs 111 to 114 in the piconet.
In FIG. 1, a closed curve 150 represents a range in which the DEVs
111 to 114 can be located so that the PNC 101 can communicate with
each of the DEVs 111 to 114. That is, in the range 150, each of the
DEVs 111 to 114 can communicate directly with the PNC 101. However,
it is not sure whether each of the DEVs 111 to 114 can communicate
directly with any one of the other DEVs 111 to 114. For example, it
is assumed that the DEVs 112 and 113 shown in FIG. 1 cannot
communicate directly with each other because of signal attenuation
due to the distance between them.
In a case where the PNC 101 is changed, by changing an operation
mode, to a DEV, which is unable to control the other DEVs, it is
necessary to transfer control rights (herein after referred to as
"PNC handover") to one of the DEVs 111 to 114. For example, it is
assumed that the possibilities of communication between the devices
provided in the piconet are classified according to levels as a
security countermeasure. Because the PNC can communicate with all
of the other devices in the piconet which the PNC joins, the PNC
handover is needed in a case where it is necessary to reduce a
security level of the PNC (e.g., a case where a person other than
an owner of the PNC temporarily uses the PNC) . Also, in a case
where the PNC finishes an operation and leaves the piconet, the PNC
handover is needed. At that time, first, a DEV (hereinafter
referred to as a PNC candidate) to be operated as a PNC, is
selected as a DEV to which control is transferred. In a case where
a plurality of PNC candidates is present, a DEV having the highest
level function and performance is selected.
In a case where the DEVs 113 and 114 are PNC candidates and the DEV
113 is higher in function and performance than the DEV 114, the PNC
101 selects the DEV 113 as a DEV to which control rights are
transferred. Subsequently, the PNC handover is performed. Thus, the
DEV 113 and the PNC 101 change operation modes, so that the DEV 113
is changed to a PNC and the PNC 101 is changed to a DEV.
FIG. 2 illustrates a positional relationship among a PNC and DEVs
after the PNC handover is performed. The PNC 201 and the DEV 215
correspond to the DEV 113 and the PNC 101 shown in FIG. 1,
respectively. A closed curve 250 represents a communicatable range
in which the DEVs can be located so that the PNC 201 can
communicate with each of the DEVs. That is, the DEV 112 is out of
the communicatable range of the PNC 201. Therefore, the DEV 112 is
forcibly disconnected from the piconet, and cannot continue to join
the piconet.
SUMMARY OF THE INVENTION
One feature of the present invention is to reduce, when a control
rights transfer process is performed in a network, the number of
network devices that cannot continue to join the network.
Another feature of the present invention is to efficiently
determine a network device to which control rights is
transferred.
According to an aspect of the present invention, a communication
control device configured to control communication among a
plurality of communication devices includes a counting unit
configured to cause each of one or more candidate devices to which
control rights of a network are transferable, from among the
plurality of communication devices, to transmit a pseudo
information signal, and to count, for each of the candidate
devices, the number of communication devices from the plurality of
communication devices having responded to the pseudo information
signal, and a determination unit configured to determine a
candidate device to which to transfer control rights of the network
based on the number of communication devices from the plurality of
communication devices having responded to the pseudo information
signal.
Further features and aspects of the present invention will become
apparent from the following detailed description of exemplary
embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate exemplary embodiments,
features, and aspects of the invention and, together with the
description, serve to explain the principles of the invention.
FIG. 1 illustrates an exemplary positional relationship among a
control device and slave devices in a piconet.
FIG. 2 illustrates an exemplary positional relationship among a
control device and slave devices after control rights is
transferred.
FIG. 3 is a block diagram illustrating an internal configuration of
a communication device.
FIG. 4 illustrates a structure of an IEEE802.15.3 communication
frame (superframe).
FIG. 5 illustrates a DEV that receives a beacon from a PNC of an
adjacent piconet.
FIG. 6 is a flowchart illustrating an exemplary operation of a PNC
during PNC handover according to a first exemplary embodiment of
the present invention.
FIG. 7 illustrates an example of a communication sequence performed
between devices during PNC handover according to the first
exemplary embodiment.
FIG. 8 illustrates an exemplary positional relationship among a
control device and slave terminals according to the first exemplary
embodiment after control rights are transferred.
FIG. 9 illustrates an example of a communication sequence performed
between devices during PNC handover according to a second exemplary
embodiment.
FIG. 10 illustrates an exemplary positional relationship among a
control device and slave devices in a piconet according to a third
exemplary embodiment of the present invention.
FIG. 11 illustrates an exemplary communication sequence performed
between devices during PNC handover according to the third
exemplary embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Various exemplary embodiments, features, and aspects of the
invention will be described in detail below with reference to the
drawings.
In the following description, a control device is referred to as a
PNC (piconet coordinator) . Devices, which do not serve as a
control device, are referred to DEVs. A network including the PNC
and the DEVs is referred to as a piconet.
First Exemplary Embodiment
Outline. In the first exemplary embodiment, a PNC causes each PNC
candidate (DEV) to transmit a pseudo information signal
(hereinafter referred to as a dummy beacon). The PNC detects
responses to the dummy beacon from the other DEVs in the piconet.
Thus, the PNC can determine a communicatable state of the PNC
candidate having transmitted the dummy beacon. The PNC determines
which PNC candidate to transfer control rights to according to the
communicatable states of the PNC candidates. Consequently, the PNC
can reduce the number of the DEVs that cannot continue to join the
piconet.
Configuration of Entire Communication System
The configuration of the entire communication system is described
below by assuming that the communication system conforms to the
IEEE802.15.3 standard, and that the positional relationship among
the PNC and the DEVs is similar to the positional relationship
illustrated in FIG. 1. That is, the PNC 101 manages the DEVs 111 to
114 as devices joining the piconet. The DEVs 112 and 113 cannot
communicate directly with each other because of signal attenuation
due to the distance between them. The DEVs 113 and 114 are PNC
candidates.
Internal Configuration of Device
FIG. 3 is a block diagram illustrating the internal configuration
of a piconet device according to the first exemplary embodiment.
The internal configuration shown in this block diagram is common to
the PNC and the DEVs. The PNC and each of the DEVs differ from each
other in operation mode due to whether the device is a control
device in the piconet.
A communication unit 301 provides a communication function. A clock
generation unit 302 generates a clock that is a timing reference of
the communication unit 301. A central processing unit (CPU) 303
executes a control program and controls an operation of the device.
A random-access memory (RAM) 304 is utilized as both a memory area,
which is used to execute the control program, and a temporary
storage area configured to store operation parameters, such as a
PNID which will be described later. In a case where the device is
the PNC, information (hereinafter referred to as a DEV list 310) on
the devices joining the piconet, which is managed by the PNC, is
temporarily stored in the RAM 304. A read-only memory (ROM) 305
stores various control programs executed by the CPU 303 and also
stores parameters such as identification addresses that will be
described later. A power supply unit 306 is used to operate each
component of the device.
Frame Structure
FIG. 4 illustrates a structure of a communication frame
(superframe) conforming to the IEEE802.15.3 standard.
A superframe 400 includes a beacon frame (BF) 410 used to control
the piconet, and periods used to perform actual data communications
between devices. The periods used to perform actual data
communications include a contention access period (CAP) 420 and a
channel time allocation period (CTAP) 430. The CTAP 430 includes a
plurality of periods (hereinafter referred to as slots) assigned to
each communication device.
The BF 410 is placed at a leading portion of the superframe 400 and
is periodically transmitted by the PNC. The BF 410 includes basic
information used to manage the piconet. The DEV can know timing of
a slot, which is used by the DEV at transmission or reception, and
a change in various setting information by receiving the BF 410.
Each DEV in the piconet acquires the periodically transmitted BF
410. This prevents an occurrence of an out-of-synchronization
condition between the DEVs.
A slot is allotted to each DEV in response to a request from a DEV
in the piconet or according to the determination by the PNC. Each
DEV performs communication in a time-sharing manner according to
slot information notified by using the BF 410. Communication
between the devices in the piconet is performed in this way to
prevent an occurrence of communication collision.
As illustrated in FIG. 4, the BF 410 includes a MAC header (MH) 411
and a beacon frame body (BFB) 412. In the MH 411, an identification
address of a signal source device is stored as SrcID. Also, an
identification address of a signal destination device is stored
therein as DestID. Also, an identification ID of the piconet is
stored therein as PNID. The BFB 412 has a region called piconet
synchronization parameters in which an identification address of
the PNC is stored as the PNC address.
Detection of Adjacent Piconet
In a case where a plurality of piconets are present and adjoining
one another, the DEV receives a plurality of beacon signals.
FIG. 5 illustrates a DEV that receives a beacon from a PNC of an
adjacent piconet. A DEV 511 joins a piconet controlled by a PNC 501
and receives a beacon from the PNC 501. The DEV 511 also receives a
beacon from a PNC 502 of the adjacent piconet.
Typically, adjacent piconets can be distinguished from each other
by using the PNIDs stored in the MH 411. However, the PNID is a
value that can be optionally set. Thus, adjacent piconets may use
the same PNID. Although the adjacent piconets can be distinguished
from each other by using the PNC address stored in the BFB 412,
normal piconet control is performed according to the PNID.
In view of such circumstances, per the IEEE802.15.3 standard, when
a DEV receives a beacon having the same PNID as the PNID of a
piconet, in which the DEV takes part, and a PNC address differing
from the PNC address of the piconet, the DEV reports the reception
of the beacon to the PNC of the piconet in which the DEV takes
part. More specifically, when a DEV 511 receives a beacon having
the same PNID as that of a PNC 501 from a PNC 502, the DEV 511
transmits an announcement signal to the PNC 501. That is, the DEV
511 transmits the announcement signal to the PNC 501 by using the
received beacon, which has a PNC address different from the PNC
address of the PNC 501, as a trigger.
Determination of Communicatable State of PNC Candidate Utilizing
Announcement Signal
The PNC can determine a communicatable state, in which the PNC
candidate is communicatable with each of other DEVs, in the
following procedure utilizing the function of an announcement
signal.
FIG. 6 is a flowchart illustrating an exemplary operation,
according to the first exemplary embodiment, performed to determine
the communicatable state, in which the PNC candidate is
communicatable with each of other DEVs, by the PNC.
In step S601, the PNC transmits a control command to a PNC
candidate. The control command is configured to cause the PNC
candidate to transmit a pseudo information signal (i.e., a dummy
beacon signal). The dummy beacon signal is a beacon signal
representing information that has the same PNID as the PNID of a
beacon signal transmitted from the PNC and that also has a PNC
address which is an identification address of the PNC candidate.
For example, the PNC 101 transmits the control command to the DEV
113.
Next, in step S602, the DEV having received the control command
transmits the dummy beacon signal. For example, the DEV 113
transmits the dummy beacon signal. As described above, a PNC
address included in information represented by this dummy beacon
signal is an identification address of the DEV 113. Because the DEV
113 joins the piconet controlled by the PNC 101, the information
represented by the dummy beacon signal has the same PNID.
Therefore, the PNID included in the information represented by this
dummy beacon signal is the same as that of a beacon signal
transmitted by the PNC 101.
In step S603, a DEV having received the dummy beacon signal
transmits an announcement signal to the PNC. That is, a DEV having
received the dummy beacon signal recognizes the dummy beacon signal
as a beacon signal transmitted from an adjacent piconet having the
same PNID. Thus, as described above in "Detection of Adjacent
Piconet", the DEV having received the dummy beacon signal transmits
the announcement signal to the PNC.
For example, the DEVs 111 and 114 can receive the dummy beacon
signal transmitted from the DEV 113. Thus, the DEVs 111 and 114
transmit the announcement signal to the PNC 101. Conversely, the
DEV 112 cannot receive the dummy beacon signal transmitted from the
DEV 113. Thus, the DEV 112 transmits no announcement signal.
In step S604, the PNC receives announcement signals from the DEVs
and counts the number of the received announcement signals
corresponding to each of the DEVs. Because the PNC can communicate
with each of the DEVs without failure, the PNC can receive
announcement signals from the DEVs at all times. For example, the
PNC 101 receives announcement signals transmitted from the DEVs 111
and 114 and counts the number of the announcement signals
corresponding to each of the DEVs 111 and 114.
In step S605, the PNC determines a communicatable state in which
the PNC candidate having transmitted the dummy beacon signal can
communicate with the other DEVs, based on information on the number
of the announcement signals corresponding to each of the DEVs,
which is calculated in step S604. Additionally, the PNC can
determine a DEV which cannot communicate with one of the other DEVs
by utilizing the DEV list 310. For example, the PNC 101 determines
that the DEV 113 can communicate with the DEVs 111 and 114 and the
PNC 101. Alternatively, the PNC determines that the DEV 113 cannot
communicate with the DEV 112. The DEV list 310 is a list of data
including identification addresses which is stored in the PNC when
the DEVs join a piconet. The detail of the DEV list 310 will be
described later.
Thus, the PNC can determine the communicatable state in which each
of the PNC candidates can communicate with the other DEVs. The PNC
determines a PNC candidate which can communicate with the largest
number of DEVs from among a plurality of PNC candidates as a device
to which to transfer control rights. Consequently, the number of
network devices which cannot continue to join a piconet can be
reduced. Alternatively, the PNC can determine a PNC candidate with
which the smallest number of DEVs cannot communicate with from
among a plurality of PNC candidates as a device to which to
transfer control rights.
Communication Sequence During PNC Handover
FIG. 7 illustrates an example of a communication sequence performed
between the devices during PNC handover according to the first
exemplary embodiment. The following communication sequence
commences by being triggered in a case where the PNC 101 needs to
change an operation mode so that the PNC is changed to a DEV, or in
a case where the PNC finishes an operation and leaves the network.
That is, the following communication sequence is started by
determining that the PNC handover is performed.
As described above, the RAM 304 stores a list of identification
addresses of the DEVs in the piconet managed by the PNC 101 and a
list of the functions and performance of each of the DEVs (i.e.,
the DEV list 310). For example, information on the functions
includes information representing whether each DEV can operate as a
PNC. Information on the performance includes information
representing the number of DEVs that each DEV can accommodate in a
piconet. The DEV list 310 is created by the PNC 101 based on
information reported from each DEV when the DEV joins the piconet.
Then, the DEV list 310 is stored on the RAM 304. The IEEE802.15.3
standard describes the DEV list 310 in detail, and thus, a detailed
description of the DEV list 310 is omitted herein.
The PNC 101 periodically transmits beacon signals to the DEVs 111
to 114 in the piconet. The PNC 101 determines, based on the
above-described DEV list 310, that the DEVs 113 and 114 are PNC
candidates. Then, the PNC 101 transmits a control command to the
DEV 113 (step S601) so as to cause the DEV 113 to transmit a dummy
beacon signal. Here, the PNC 101 suppresses the transmission of a
beacon signal in a superframe time subsequent to a superframe time
in which the control command is transmitted. As long as a slot is
adapted so that the DEV 113 can receive the slot, the PNC 101 may
transmit a control command in an optional slot.
The DEV 113 then transmits a dummy beacon signal to the devices in
the piconet (step S602) . Here, the DEV 113 transmits the dummy
beacon signal in a beacon time of a superframe time subsequent to
the superframe time in which the DEV 113 receives the control
command. As described above, the PNC 101 suppresses the
transmission of a beacon signal in a superframe time subsequent to
the superframe time in which the DEV 113 receives the control
command. Thus, no collision of signals occurs.
The DEVs 111 and 114 having received the dummy beacon signals
transmit announcement signals to the PNC 101 (step S603) However,
the DEV 112 cannot receive the dummy beacon signal. Accordingly,
the DEV 112 transmits no announcement signals. Also, because each
DEV transmits an announcement signal in the CTA period 430,
collision of each announcement signal with another signal does not
occur. Then, the PNC 101 receives the announcement signals from the
DEVs and counts the number of announcement signals received from
the DEVs.
FIG. 7 illustrates an example in which the announcement signals are
transmitted in the superframe in which the dummy beacon signal is
transmitted. However, the transmission of announcement signals and
the calculation of the number of received announcement signals can
be performed utilizing a plurality of superframe periods.
The PNC 101 can determine according to a result of counting the
number of announcement signals that in a case where control rights
is transferred to the DEV 113, the DEV 112 cannot continue to join
the piconet.
Subsequently, the PNC 101 checks the communicatable state of the
DEV 114 in a similar procedure. That is, the PNC 101 transmits a
control command to the DEV 114 (step S601) so as to cause the DEV
114 to transmit a dummy beacon signal. Then, the DEV 114 transmits
a dummy beacon signal to the devices in the piconet (step S602).
Then, the DEVs 111, 112, and 113 transmit announcement signals to
the PNC 101 (step S603).
The PNC 101 can determine, according to a result of counting the
number of announcement signals, that in a case where control rights
is transferred to the DEV 114, all of the DEVs can continue to join
the piconet.
Thus, the PNC 101 checks the communicatable state of each of the
DEVs 113 and 114 as described above. Subsequently, the PNC 101
selects the DEV 114 which can communicate with the largest number
of DEVs to be a device to which to transfer control rights. Then,
PNC handover is performed on the selected DEV 114. Upon completion
of performing the PNC handover, the DEV 114 starts to function as a
new PNC 801 and periodically transmits a beacon signal. Meanwhile,
the PNC 101 continues to join the piconet as a DEV 815.
Alternatively, the PNC 101 leaves the piconet. Since the PNC
handover conforms to the IEEE802.15.3 standard, a detailed
description of the handover is omitted herein.
With the above procedure, the PNC determines a DEV to which to
transfer control rights. Consequently, the number of devices which
leave the piconet due to the PNC handover can be reduced to a
minimum.
FIG. 8 illustrates an exemplary positional relationship among the
PNC and the DEVs according to the first exemplary embodiment after
the PNC handover. As can be seen from FIG. 8, all of the devices
that joined the piconet before the PNC handover is performed can
continue to join the piconet.
As described above, the communicatable state in which each of the
PNC candidates can communicate with the other DEVs is checked.
Then, a DEV to which to transfer control rights is determined based
on a result of checking. Consequently, the number of devices which
leave the piconet due to the PNC handover can be reduced to a
minimum. Also, the utilization of the function of the announcement
signals enables efficient and quick processing. Additionally, the
utilization of the function of the announcement signals allows for
mounting the devices while suppressing a scale of change to a
device conforming to the IEEE802.15.3 standard.
Second Exemplary Embodiment
Outline
According to a second exemplary embodiment, a PNC causes a PNC
candidate to perform broadcast transmission of a dummy beacon
signal. The second exemplary embodiment differs from the first
exemplary embodiment in that the CTA period 430 is utilized as a
time at which the broadcast transmission is performed. The
configuration of the entire communication system and the internal
configuration of each device are similar to those of the first
exemplary embodiment. Therefore, a description of the configuration
of the entire communication system and the internal configuration
of each device is omitted herein.
Communication Sequence During PNC Handover
FIG. 9 illustrates an example of a communication sequence performed
between the devices during PNC handover according to the second
exemplary embodiment. The following communication sequence
commences by being triggered in a case where the PNC 101 needs to
change an operation mode so that the PNC is changed to a DEV, or in
a case where the PNC finishes an operation and leaves the network.
That is, the following communication sequence is started by
determining that the PNC handover is performed.
As described above, the RAM 304 stores a list of identification
addresses of the DEVs in the piconet managed by the PNC 101 and a
list of the functions and performance of each of the DEVs (i.e.,
the DEV list 310). For example, information on the functions
includes information representing whether each DEV can operate as a
PNC. Information on the performance includes information
representing the number of DEVs that each DEV can accommodate in
the piconet. The DEV list 310 is created by the PNC 101 based on
information reported from a DEV when the DEV joins the piconet, and
then the DEV list 310 is stored in the RAM 304.
The PNC 101 periodically transmits beacon signals to the DEVs 111
to 114 in the piconet. The PNC 101 determines, according to the
above DEV list 310, that the DEVs 113 and 114 are PNC candidates.
Then, the PNC 101 transmits a beacon signal, to which a slot for
performing broadcast transmission is assigned, to the DEV 113.
Typically, slots are assigned by the PNC according to a request
from the DEV. Also, identification addresses representing a
transmitting device and information representing a receiving device
are typically designated as information representing each slot. In
a case where an identification address representing a broadcasting
(simultaneous-reception-by-all-devices) address is designated as an
identification address of a receiving device, all of the devices
other than the transmitting device in the piconet operate as being
in a receivable state.
The DEV 113 performs broadcast transmission of a dummy beacon
signal to the devices in the piconet. The DEV 113 performs the
broadcast transmission of a dummy beacon signal according to a
criterion that although the DEV 113 does not request, a slot for
broadcast is allotted by the PNC 101. In the present exemplary
embodiment, the transmission is performed by the DEV 113 in a
superframe time in which the beacon signal is received. As
described above, in this superframe time, the other DEVs and the
PNC 101 are in a reception condition. Thus, collision of signals
does not occur. The broadcast frame is similar in frame structure
to the beacon frame and differs therefrom in that an identification
address of the DEV 113 is stored as a PNC address.
The DEVs 111 and 114 having received the dummy beacon signals
transmit announcement signals to the PNC 101. However, the DEV 112
cannot receive the dummy beacon signal. Thus, the DEV 112 transmits
no announcement signals. Also, because the DEV transmits an
announcement signal in the CTA period 430, collision of each
announcement signal with another signal does not occur. Then, the
PNC 101 receives the announcement signals from the DEVs and counts
the number of announcement signals received from the DEVs.
FIG. 9 illustrates an example in which the announcement signals are
transmitted in a superframe subsequent to a superframe in which the
dummy beacon signal is transmitted. However, the transmission of
announcement signals and the calculation of the number of received
announcement signals can be performed utilizing a plurality of
superframe periods.
The PNC 101 can determine, according to a result of counting the
number of announcement signals, that in a case where control rights
are transferred to the DEV 113, the DEV 112 cannot continue to join
the piconet.
Subsequently, the PNC terminal 101 checks the communicatable state
of the DEV 114 in a similar procedure. That is, the PNC 101
transmits a beacon signal to which a slot for broadcast
transmission of a dummy beacon signal is allotted. Then, the DEV
114 performs broadcast transmission of a dummy beacon signal to the
devices in the piconet. Next, the DEVs 111, 112, and 113 having
received the dummy beacon signals transmit announcement signals to
the PNC 101.
The PNC 101 can determine, according to a result of counting the
number of announcement signals that in a case where control rights
are transferred to the DEV 114, that all of the DEVs can continue
to join the piconet.
Thus, the PNC 101 checks the communicatable state of each of the
DEVs 113 and 114 as described above. Subsequently, the PNC 101
selects the DEV 114 which can communicate with the largest number
of DEVs to be a device to which to transfer control rights. Then,
PNC handover is performed on the selected DEV 114. As previously
indicated, the procedure for the PNC handover conforms to the
IEEE802.15.3 standard. Upon completion of performing the PNC
handover, the DEV 114 starts to function as a new PNC and
periodically transmits a beacon signal. Meanwhile, the PNC 101
continues to join the piconet as a DEV. Alternatively, the PNC 101
leaves the piconet.
With the above procedure, the PNC determines a DEV to which to
transfer control. Consequently, the number of the devices which
leave the piconet due to the PNC handover can be reduced to a
minimum.
As described above, the communicatable state in which each of the
PNC candidates can communicate with the other DEVs is checked.
Then, a DEV to which to transfer control rights is determined
according to a result of checking. Consequently, the number of
devices which leave the piconet due to the PNC handover can be
reduced to a minimum. Also, the communicatable state in which each
of the PNC candidates can communicate with the other DEVs can
quickly be checked. Additionally, the transmission of a dummy
beacon signal can be performed by utilizing the CTA period 430
assigned to each of the DEVs. Thus, collision of dummy beacon
signals can be prevented. Also, the assignment of a broadcasting
slot enables a DEV to recognize the transmission of the dummy
beacon signal.
Third Exemplary Embodiment
Outline
A third exemplary embodiment is directed to a method of efficiently
determining a device to which to transfer control rights in a case
where three or more PNC candidates are present. More specifically,
priorities are preliminarily set at the PNC candidates, then, the
PNC candidate first specified as a device which can assure a
communication path therefrom to each of the devices in an existing
piconet is determined to be a device to which to transfer control
rights. Consequently, even in a case where a large number of PNC
candidates are present, PNC handover can quickly be performed on an
appropriate device. The internal configuration of each device is
similar to that of the device in the first exemplary embodiment.
Therefore, a description of the internal configuration of each
device is omitted herein.
Configuration of Entire Communication System
The communication system of the present exemplary embodiment is
described below, where the communication system conforms to the
IEEE802.15.3 standard.
FIG. 10 illustrates an exemplary positional relationship among the
PNC and the DEVs in the piconet according to the third exemplary
embodiment. That is, the PNC 1001 manages the DEVs 1011 to 1016 as
devices joining the piconet. The DEVs 1013 and 1016 cannot
communicate directly with each other because of signal attenuation
due to the distance between them. The DEVs 1013 to 1016 are PNC
candidates.
Communication Sequence during PNC Handover
FIG. 11 illustrates an exemplary communication sequence performed
between the devices during PNC handover according to the third
exemplary embodiment. The following communication sequence
commences by being triggered in a case where the PNC 1001 needs to
change an operation mode so that the PNC 1001 is changed to a DEV,
or in a case where the PNC 1001 finishes an operation and leaves
the network. That is, the following communication sequence is
started by determining that the PNC handover is performed.
The PNC 1001 has a list of identification addresses of the DEVs in
the piconet managed by the PNC 1001 and a list of the functions and
performance of each of the DEVs (the DEV list 310). For example,
information on the functions includes information representing
whether each DEV can operate as a PNC. Information on the
performance includes information representing the number of DEVs
that each DEV can accommodate in the piconet. The DEV list 310 is
created by the PNC 1001 according to information reported from a
DEV when the DEV joins the piconet. Then, the DEV list 310 is
stored in the RAM 304. The IEEE802.15.3 standard describes the DEV
list 310 in detail, thus a detailed description of the DEV list 310
is omitted herein.
The PNC 1001 periodically transmits beacon signals to the DEVs 1011
to 1016 in the piconet. The PNC 1001 determines, according to the
DEV list 310, that the DEVs 1013 to 1016 are PNC candidates.
Subsequently, prioritization is performed on the DEVs 1013 to 1016
to determine an order according to which an operation of checking a
communicatable state is performed on the DEVs 1013 to 1016. The
prioritization is performed according to the information on the
function and performance, which includes the information
representing the number of DEVs that each DEV can accommodate in
the piconet. Here, the DEVs are arranged in descending order of
priority, that is, the DEV 1013, the DEV 1014, the DEV 1015, and
the DEV 1016.
First, the PNC 1001 transmits a control command to the DEV 1013
(step S601) so as to cause the DEV 1013 to transmit a dummy beacon
signal. The PNC 1001 suppresses the transmission of a beacon signal
in a superframe time subsequent to a superframe time in which the
control command is transmitted. As long as a slot is adapted so
that the DEV 1013 can receive the slot, the PNC 1001 can transmit a
control command in an optional slot.
The DEV 1013 transmits a dummy beacon signal to the devices in the
piconet (step S602) . The DEV 1013 transmits the dummy beacon
signal in a beacon time of a superframe time subsequent to the
superframe time in which the DEV 1013 receives the control command.
As described above, the PNC 1001 suppresses the transmission of a
beacon signal in the superframe time subsequent to the superframe
time in which the DEV 1013 receives the control command. Thus, no
collision of signals occurs.
The DEVs 1011, 1012, 1014, and 1015 having received the dummy
beacon signals transmit announcement signals to the PNC 1001 (step
S603) . However, the DEV 1016 cannot receive the dummy beacon
signal. Thus, the DEV 1016 transmits no announcement signals. Also,
because each DEV transmits an announcement signal in the CTA period
430, collision of each announcement signal with another signal does
not occur. Then, the PNC 1001 receives the announcement signals
from the DEVs and counts the number of announcement signals
received from the DEVs.
FIG. 11 illustrates an example in which the announcement signals
are transmitted in the superframe in which the dummy beacon signal
is transmitted. However, the transmission of announcement signals
and the calculation of the number of received announcement signals
can be performed utilizing a plurality of superframe periods.
The PNC 1001 can determine, according to a result of counting the
number of announcement signals, that in a case where control rights
are transferred to the DEV 1013, the DEV 1016 cannot continue to
join the piconet.
Subsequently, the PNC terminal 1001 checks the communicatable state
of the DEV 1014 in a similar procedure. That is, the PNC 1001
transmits a control command to the DEV 1014 (step S601) so as to
cause the DEV 1014 to transmit a dummy beacon signal. Subsequently,
the DEV 1014 transmits a dummy beacon signal to the devices in the
piconet (step S602). Then, the DEVs 1011, 1012, 1013, 1015, and
1016 transmit announcement signals to the PNC 1001 (step S603).
The PNC 1001 can determine, according to a result of counting the
number of announcement signals, that in a case where control rights
are transferred to the DEV 1014, all of the DEVs can continue to
join the piconet. Thus, the PNC 1001 selects the DEV 1014 as a
device to which to transfer control rights. This is because the
checking of the communicatable states of the DEVs 1015 and 1016
serving as the remaining PNC candidates does not affect the
selection of a device to which to transfer control.
In a case where PNC candidates communicatable with all of the DEVs
are not present, the checking of the communicatable state is
performed on all of the PNC candidates. Then, a DEV, e.g., the DEV
1014, having the largest number of DEVs communicatable with the DEV
1014 as compared with the other DEVs is determined as a device to
which to transfer control rights.
The procedure for the PNC handover conforms to the IEEE802.15.3
standard, and thus a detailed description thereof is omitted
herein. Upon completion of the PNC handover, the DEV 1014 starts to
function as a new PNC and periodically transmits a beacon signal.
Meanwhile, the PNC 1001 continues to join the piconet as a DEV.
Alternatively, the PNC 1001 leaves the piconet.
With the above procedure, the PNC determines a DEV to which to
transfer control rights. Consequently, the number of devices which
leave the piconet due to the PNC handover can be reduced to a
minimum. Additionally, in a case where a large number of PNC
candidates are present, the time required to perform a selection
operation can be reduced considerably.
In the foregoing description of the present exemplary embodiment,
the prioritization to determine the order according to which an
operation of checking a communicatable state is performed, is
performed according to the information on the function and
performance, which includes the information representing the number
of DEVs that each DEV can accommodate in the piconet. Performance
of the prioritization is not limited to this type of information,
and the prioritization can be performed according to any kind of
information that would enable the DEVs to continue to join the
piconet.
For example, the prioritization can be performed according to
reception level information representing a reception level of a
radio wave received from each DEV. Generally, the higher the
reception level is of a radio wave received by the PNC 1001 from a
DEV, the closer the DEV is physically to the PNC 1001. Thus, the
DEV transmitting a radio wave with a high reception level at the
PNC 1001 can be expected to have a communicatable range close to
the communicatable range of the PNC 1001.
Other Exemplary Embodiments
The above described exemplary embodiments can be implemented by
causing a system or an apparatus to read and execute program code
directly or remotely supplied thereto. Accordingly, the program
code itself installed in the computer to implement the functions
and processes of the present invention on computers is included in
the scope of the present invention.
In such a case, as long as programs have the functions, the
programs having any form can be employed. For example, object code,
program code executed by an interpreter, and script data supplied
to an operating system (OS) can be employed.
Recording media for supplying the program include, for example, a
flexible disk, a hard disk, an optical disk, a magneto-optical disk
(MO), a compact disk read only memory (CD-ROM), a magnetic tape, a
nonvolatile memory card, a read-only memory (ROM), and a digital
versatile disk read only memory (DVD-ROM).
The program read from the recording media can be written on a
memory on an expansion board inserted into the computer or on an
expansion unit connected thereto. According to instructions issued
from the program, a CPU or the like provided on the expansion board
or the expansion unit performs part or all of actual processes to
implement the above functions of the exemplary embodiments.
Thus, the present invention can provide techniques enabled to
reduce, when a control rights transfer process is performed in a
network, the number of network devices that cannot continue to join
the network.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all modifications, equivalent structures, and
functions.
This application claims priority from Japanese Patent Application
No. 2005-317113 filed Oct. 31, 2005, which is hereby incorporated
by reference herein in its entirety.
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